I am trying to add trend lines to my chart. however, when right clicking and selecting the measure I get the following error message:

Although trend lines are requested, a trend line model cannot be computed. The documentation describes when trend models can be computed. Typically, you need two quantitative, axes or one quantitative axis and one ordinal axis that supports a uniform quantitative interpretation.

Has anyone comes across this problem before and found a quick resolution for this?

On the Columns shelf, replace Download Month with "My Date". On the Columns shelf, click the My Date pill and change it from Discrete (blue colored) to Continuous (Green colored). On the Columns Shelf, click the My Date pill again, and change it's datepart to Month.